1. Technical Field
The disclosure substantially relates to clamping devices, and more particularly to a clamping device for clamping a lens preform.
2. Description of Related Art
Currently, plastic lenses are widely used in consumer electronic products, for example, digital cameras, as they are cheap and simple to manufacture.
In general, in manufacturing the plastic lenses, a lens preform including the plastic lenses is formed by applying a plastic injection molding process, and then the plastic lenses can be cut from the lens preform. Referring to FIG. 10, a typical lens preform 40 is shown. The lens preform 40 may include four plastic lenses 42, a sprue 44, and four runners 46. Each of the runners 46 is connected to the sprue 44. The four plastic lenses 42 are connected to the four respective runners 46.
In general, before the plastic lenses 42 can be cut away from the runners 46, a clamping device 50 as shown in FIG. 11 is provided to clamp the lens preform 40. The clamping device 50 has a first groove 52 and a second groove 54 defined at a top surface 51 thereof. The first groove 52 intersects and communicates with the second groove 54. In use, the runners 46 of the lens preform 40 are received in the first groove 52 and the second groove 54. A knife 60 can be provided to cut the plastic lenses 42 away from the runners 46.
However, it is very difficult to for the clamping device 50 to clamp the lens preform 10 firmly as the lens preform 10 may vibrate in the first and the second grooves 52 and 54. In that case, the plastic lenses 42 cannot be properly cut from the lens preform 10.
Therefore, what is needed is a clamping device that can overcome the described limitations.